p‑STAT3 influences doxorubicin and etoposide resistance of A549 cells grown in an in vitro 3D culture model

Tumor microenvironment undoubtedly has a significant impact on therapeutic responses. Abundant evidence suggests that the 3D in vitro culture holds great promise for drug discovery and development by bridging the gap between conventional 2D culture and animal models. The present study described 3D basement membrane culture of A549 cells, which mimics the complex 3D arrangement of tumors in vivo and elucidates the underlying mechanisms of microenvironmental influences on cellular functions and therapeutic efficacy. A549 cells cultured in 3D undergo G(0)/G(1) phase arrest and decreased migratory and invasive capacity, indicating dormant cell characteristics. Hypoxia, apoptosis and stemness were demonstrated in the A549 cells in 3D architecture compared with the 2D-cultured counterparts. More importantly, cells in the 3D environment exhibited increased resistance to different classes of anticancer agents. Western blotting revealed changes in the levels of key cancer-associated pathways, phosphorylated (p)-STAT3, p-ERK, and p-Akt, in response to 3D culture compared with 2D monolayer culture. Notably, mechanistic analysis using specific inhibitors showed that the STAT3 inhibitor overcomes the 3D culture-induced doxorubicin and etoposide resistance. These results implicated an important role of p-STAT3 in conferring chemoresistance in 3D-cultured A549 cells, as well as the use of STAT3 inhibitor as a potential chemosensitizer to improve drug sensitivity. Thus, 3D culture systems, that more closely resemble in vivo tumor biology, may be more effective models in searching for novel chemotherapeutic agents and therapeutic targets for cancer treatment.